Oil switch



J1me 1930- Y A. WICYHERT 1,765,575

, OIL SWITCH Filed May 15, 1926 provision of Patented June 24, 1930 UNITED srArss ALFRED WICHERT, OF MANNI-IEIM-NEUOSTHEIM, GERMANY, ASSIGNOR TO AKTIEN- .GESELLSCHAIFT BROVN BOVERI 8:, 011, OF BADEN, SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZERLAND OIL SWITCH Application filed May 13, 1926, Serial No. 108,766, and in Germany July 24, 1925.

'larly to high voltage switches designed to be opened in event ofoverloads, such as may occur from grounds or short circuits in the system protected by the switch.

The general object of the invention is the a construction which is protected against rupture or explosion of the container incident to the opening of the switch whenunder heavy load.

A more specific object is the provision of a construction which will quickly vent gases 7 generated in the body of oil incident to such an occurrence.

A further object is the provision of a construction having the characteristics specified above, and which will tend to prevent flashing over between the external terminals of the switch from gases generated incident to an opening of the switch under heavy load.

Other and further objects will be pointed out or indicated hereinafter or obvious to one skilled in the art upon an understanding of the invention.

In the drawing forming a part of this specification I show one form in which the invention may be embodied, but it is to be understood that this is presented for illustration only, and is not to be accorded any interpretation limiting the claims short of the true and most comprehensive scope of the invention in the art.

The figure represents a sectional elevation oi an oil switch containing the invention.

According to the most recent investiga tions, the breaking of large amounts of ower under oil is accompanied by the formation of a bubble of gas which surrounds the contacts. If this gas bubble is not allowed to expand with suflicient freedom its pressure and consequently the pressure in the oil container rises to an excessive value and may lead to the explosion of the switch.

The expansion vents usually fitted above the oil surface, and intended to permit the escape'of the gas-air mixture in the event of its being ignited, because of space limitations are usually far too small to be of any use in discharging the layer of oil above the gas bubble should a very heavy shortcircuit occur.

According to the invention, an excessive rise of pressure in the interior of the oil switch is prevented by venting or pricking the bubble as soon as it has reached a certain size. For this purpose re-entrant, funnel-shaped structures are incorporated so in the switch, the converging end of the tunnel approaching the neighbourhood of the switch contacts around which the bubble is formed. As a result of the special form which may be given to this structure, the oil level in the funnel itself and consequently the resistance opposed to the escape of the gases can be made much less than with the usual cylindrical vent tubes employed. Hence, for this reason also the rise of pressure and the quantity of oil thrown out will be substantially less than with oil switches of the usual design.

The drawing shows a possible form of the invention in which the switch tank is designated 10, the terminal insulating bushings 11, the external terminals 12, and the internal stationary terminals 1d. The movable contacts 15 are carried on a movable bridge 16, and are moved into and out of so contact with the contacts 15 by raising and lowering of said bridge by the rod 17. In the top of the tanlr is a venting opening 18, from which extends inwardly a contracting venting conduit 19, such as the funnel shown arranged above the movable contact bridge 16 of the switch. There is no objection to employing insulating material for the funnel, particularly the smaller end adjacent the contacts, thus preventing any possibility of a flash over to the funnel. To prevent loss of oil, a bafile plate 20 may be arranged at a suitable distance from the mouth of the funnel. A bailie plate or this kind also serves to keep. the gases released by an explosion away from the conductors and reduces the possibility of a flash-over between terminals being caused thereby. Finally,when the switches are to be installed out of doors or on locomotives, for

example, a valve 21 may be arranged in the mouth of the funnel to prevent the ingress of water. As it is acknowledged that the rise of pressure is not only dependent on the ease with which the oil can escape but may also be diminished to a large extent by the use of expansion chambers, such chambers 22 communicating with the interior of the switch may be incorporated inthe design. lnorder that there may be no danger from the accumulation of air-gas mixtures in the expansion chambers, these may be provided with valves 24 according to the usual practice.

In installation of the device, the oil chamber is filled with oil'to a proper level over the contacts, but the level within the venting conduit need not be so hi h as the general oil level in the chamber i? the latter is air tight, as by filling it full and subsequently withdrawing a portion through the ventmg conduit, the air pressure on the surface of the column in the latter and the reduced pressure within the rmeptacle will enable the column to hold a lower level than that of the oil in the tank. Upon the forming of a gas bubble near the contacts, as by a heavy dischar e on opening of the swltch, the bubble wifiquickly reach the submer ed end of the venting conduit, and the gas nd immediate escape through the latter.

\Vhat I claim is:

1. The combination with an oil switch in cluding a casing and switch contacts disposed therein, .of a contracting venting member having its smaller end opening adjacent the contacts and its larger end opening exteriorly of the casing.

2. In an oil switch, a receptacle for oil provided above the normal oil level therein with a vent opening, switch contacts disposed in the receptacle below said level, and a venting conduit of varying cross-sectional area communicating at its larger end with said opening, the smaller end of said conduit being arranged below said level and in proximity to said contacts.

3. The combination with an oil switch includin an oil casing provided above the norma .oil level therein with a vent opening, spaced switch contacts dis osed in the casing a given distance below sald level, and a movab e switch member for connecting and disconnectin said contacts, of a venting conduit having one end thereof disposed intermediate said contacts and below said level by to said distance, the other end of said conduit communicati with said opening.

4. The combination with an oil switch including an oil casing provided above the normal oil level therein with a vent opening, spaced switch contacts disposed in the casing a given distance below said level, and a movab e switch member for connecting thereof to a an amount equal substantially thereof to a pointalong said-conduitanap;

preciable distance above said level.

5. The combination with an oilfiwitch including an oil casing provided above the normal oil level therein with a vent o ening, spaced switch contacts disposed in t e casing a given distance below said level, and a movable switch member for connecti and disconnecting said contacts, of a refling conduit havingsone endthereof disposed intermediate said contacts and below said level .by an amount equal substantially to said distance,.the other end of said conduit communicating with saidopening the crosssectional area of said conduit increas' gradually from said first-mentioned en int along said conduit an appreciable distance above said level, a valve seat extending across and supported within said conduit at a point above the level therein, and a check valve seating on said seat and opening with the prcssurein 6. In an oil switch, a casing, spaced switch contacts dis used in said casing below the normal .oil evel therein, and a ventmg conduit having one end thereof disposed said casing.

one

intermediate said contacts and below said level.

In testimony --whereof I have hereunto subscribed my name at Stuttgart on the 22nd day of March, A. D. 1926. y

ALFRED WICHERT. 

